Chemical mechanical polishing (CMP) compositions and methods for polishing (or planarizing) the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries, CMP slurries, and CMP compositions) for polishing metal layers (such as tungsten) on a semiconductor substrate may include abrasive particles suspended in an aqueous solution, chemical accelerators such as oxidizers, chelating agents, and the like, and corrosion/etch inhibitors for reducing the rate at which the metal etches in the CMP slurry.
In tungsten plug and interconnect processes, tungsten is generally deposited over a dielectric and within openings formed therein. The excess tungsten over the dielectric layer is then removed during a CMP operation to form tungsten plugs and interconnects within the dielectric. As semiconductor device feature sizes continue to shrink, meeting device requirements including planarity and defect requirements has become more difficult in CMP operations such as tungsten CMP operations. For example, slurry induced defects including excessive localized corrosion can reduce device yields. Excessive array erosion, localized erosion, and tungsten plug and line recessing, can also compromise overall electrical performance and reduce device yields.
Commercially available tungsten CMP slurries commonly make use of a hydrogen peroxide oxidizer. While there are many advantages to the use of hydrogen peroxide, it is known to contribute to excessive tungsten etching in certain CMP operations. There remains a need in the industry for tungsten CMP slurries (or compositions) that are less corrosive towards tungsten. Moreover, as is well known in the art, the semiconductor industry is subject to continuing and severe downward pricing pressure that extends to the CMP consumables themselves (e.g., to the CMP slurries and pads). Such pricing pressure poses a challenge to the slurry formulator as the pressure to reduce costs often conflicts with the desired slurry performance metrics. Thus, there is also a real need in the industry for CMP slurries that are stable and that provide high throughput at reduced overall costs.